In order to protect the electrical connection between a conductive element and an electrical cable carrying large amounts of current, electrically-insulating casings of a terminal connector are used to surround the electrical connection.
It is known in the prior art to make such casings out of porcelain, laminated plastic paper, or finely ground quartz-filled casting resin. These prior-art materials, however, have many disadvantages among which is that they have a comparatively low resistance to mechanical forces and require relatively expensive mounting arrangements in order for them to safely withstand such mechanical forces.
The material used in the prior art terminal connectors is also disadvantageous, because it makes the terminal connector very heavy inasmuch as the walls of the casing themselves are necessarily very thick in order to absorb these mechanical forces. Moreover, the relatively thick walls have prevented the casings from being easily placed in an oil-filled outer housing.
It is well known to construct inner and outer collars on porcelain casings. However, the mechanical tolerances of these collars are difficult to maintain due to the unavoidable shrinking of the procelain casings after manufacture. In such porcelain casings, shims or pads must be provided intermediate the casing and the mounting arrangement in order to counter the effects of the wrong-sized mechanical tolerances.
Moreover, the lack of precision in manufacturing porcelain casings means that adequate sealing of the interior of the casing is not possible.